Plate Nº 49 · recorded October 30, 2026
Space & AstronomyReported finding
Smithsonian's Lumina Simulation Recreates the Universe's First 2 Billion Years
Scientists built Lumina, the largest cosmological radiation hydrodynamics simulation ever, spanning 1.5 billion light-years to test theories against JWST and Roman telescope data.
By Elena Vasquez4 min read726 words
In brief
- Lumina recreates the universe's first 2 billion years after the Big Bang.
- The simulation spans a cube roughly 1.5 billion light-years on each side, over 100 times larger than earlier comparable projects.
- It ran on more than 15,000 GPUs on Frontier at Oak Ridge National Laboratory.
- The research was published October 27, 2026, in Monthly Notices of the Royal Astronomical Society.
- It is the first simulation of its kind to track helium reionization as it unfolds.
A simulation spanning 1.5 billion light-years of virtual space has recreated the universe's first 2 billion years, and it's the largest project of its kind ever built. Researchers at the Center for Astrophysics | Harvard & Smithsonian call it Lumina, and they published the work October 27, 2026, in Monthly Notices of the Royal Astronomical Society.
Lumina exists for one practical reason: to help astronomers interpret what NASA's James Webb Space Telescope (JWST) and Nancy Roman Space Telescope are actually seeing when they peer at the early cosmos.
"With JWST, the early universe has become an exciting new frontier in astrophysics," said lead author Oliver Zier, an ITC Fellow at the Center for Astrophysics | Harvard & Smithsonian. "To understand what we are seeing with this telescope, we need to translate our theories into detailed predictions."
How does the simulation work?
Lumina is the largest cosmological radiation hydrodynamics simulation ever produced. In plain English, that means it uses supercomputers to calculate how gas, dark matter, and radiation pushed and pulled on one another as the young universe took shape.
Dark matter is the invisible material that outweighs ordinary matter roughly five to one. Radiation hydrodynamics is the physics of how light and gas interact. Put both into code, run it long enough, and you get a replay of cosmic infancy.
The virtual universe covers more than 100 times the volume of earlier comparable projects, a cube about 1.5 billion light-years on each side. That scale matches the vast regions today's most advanced telescopes can survey, so simulated and observed universes can be compared directly.
The team didn't stop at volume. Lumina also models, for the first time in a simulation of this kind, helium reionization — the process in which energetic radiation strips electrons off helium atoms. Crucially, it follows that transformation as it happens while also tracking how it reshapes the surrounding gas. That opens a window onto the relationship between growing galaxies, their radiation, and the gas between them.
"For the first time, we can follow along as both hydrogen and helium changed into their modern form across such an enormous volume of the universe, while still resolving the galaxies and other luminous objects driving that transformation," said co-author Aaron Smith, an assistant professor of physics at the University of Texas at Dallas.
What hardware does it take?
Plenty. The team ran Lumina on more than 15,000 graphics processing units on Frontier, one of the world's fastest supercomputers, housed at Oak Ridge National Laboratory in Tennessee.
That power let the researchers simulate a huge region without sacrificing fine detail. Lumina can track the cosmos' broad evolution and still zoom in on processes behind the formation of stars, galaxies, and black holes.
Why does it matter for telescopes?
Modern astronomy runs on a loop. Theorists build simulations that predict how the universe should behave. Telescopes observe how it actually behaves. When the two agree, confidence in current physics grows.
When they disagree, things get interesting. Unexpected mismatches may point to physical processes scientists haven't yet fully understood — or to gaps in the universe's fundamental laws as we know them.
Researchers plan to use Lumina to study several open questions:
- How gas moves between galaxies
- How radiation left over from the Big Bang shaped cosmic structures
- Why some regions formed stars at especially high rates
By placing those predictions alongside observations from JWST, the Roman Space Telescope, and other instruments, scientists hope to assemble a fuller picture of the universe's earliest chapters. Any gap between the simulated cosmos and the real one could reveal where current theories need refining — or replacing.
What's the takeaway?
Lumina gives astronomers a benchmark: a detailed, large-scale prediction of the early universe against which real telescope data can now be tested.
Zier, for one, sounded relieved to see years of work pay off. "After several years of work, with plenty of ups and downs, it is incredibly rewarding to see the simulation results and watch our predictions come to life in video," he said.
"We feel incredibly fortunate to be building simulations like Lumina," Smith added.
The full author team includes Zier, Smith, Xuejian Shen, Rongrong Liu, Rahul Kannan, Sonja M. Koehler, Volker Springel, Rüdiger Pakmor, Mark Vogelsberger, Teodora-Elena Bulichi, and Lars Hernquist (DOI: 10.1093/mnras/stag1469).
via si.edu (Original)
More from Elena Vasquez
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Correspondent covering money, funding and market shifts around general science news at SciBeat.
288 articles
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